JPS621399A - Acoustic circuit for underwater acoustic transducer - Google Patents

Abstract

PURPOSE:To constitute a small-sized acoustic filter for low frequency with good processability by laminating elastic bodies having close grooves and through-holes while bringing closely them into contact with one another. CONSTITUTION:A narrow hole offering an acoustic inertance is constituted as a series of paths from a through-hole 2a of an enclosure 2 to grooves 3b of an acoustic circuit 3 and grooves 4b and a through-hole 4a of an acoustic circuit 4, and an acoustic oil 8 is packed from the inside of the enclosure 2 to that of a diaphragm 7. Discoid grooves acoustic circuits 3 and 4 are brought into contact with each other and are laminated and fixed, and a series of paths from the joint part including the through-hole 4a to the through-hole 2a function equivalently to a metallic narrow tube having length of these extended paths.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an acoustic circuit for an underwater acoustic transducer used for imparting low-frequency acoustic filter characteristics to a deep-depth electroacoustic transducer used underwater. Regarding.

[Conventional technology]

Conventional technology includes high-frequency deep-depth acoustic circuits.

FIG. 6 is a sectional view showing an example of a conventional high frequency/deep depth acoustic circuit. This is the electric f4 as shown in FIG.
# The inner surface of the transducer 24 for conversion is attached to the support 25 and 7 langes 26
28, a through hole 26af is provided in the seventh flange 26, and a metal tube 27 is further attached to the through hole 26a.

In this type of acoustic circuit, the acoustic inertance is determined by the through hole 26a.
The pores of the medium metal tube 27 and the acoustic compliance of the vibrator 24. It is formed by a cavity surrounded by the struts 25 and 7 and the flange 26 and 28, and basically constitutes an acoustic filter that cuts off high frequencies and passes all low frequencies. In other words, for example, the cross-sectional area of the through hole 26a S.

Length 24. If the volume of the cavity is ■, the specific gravity of the sound wave propagation medium filled inside each cavity, generally acoustic oil, is p, and the speed of sound is C, then the acoustic inertance LA and acoustic compliance CA are as follows (7) 11) (2) Expressed like 2〇.

When the sound pressure and particle velocity of the acoustic system correspond to the voltage and current of the electric system, respectively, the acoustic inertance LA and the acoustic compliance CA correspond to the inductive inductance and capacitance of the electric system, respectively. A similar equivalent circuit is shown in FIG.

From the equivalent circuit in Figure 7, this acoustic filter has a cutoff frequency fc shown in equation (3), and sound waves with frequencies higher than the cutoff frequency are blocked by this acoustic circuit, and sound waves with frequencies lower than the cutoff frequency are blocked by this acoustic circuit. pass through.

At cutoff frequency fC, ゛ constitutes a resonant system with acoustic inertance LA and acoustic co/preliance C, and the amplitude expansion rate of this resonance, that is, acoustic Q, is expressed as follows, where RA is the acoustic resistance due to the viscous resistance of the sound wave propagation medium, etc. (The relationship is as shown in the four-part equation.

・・・・・・・・・・・・ (4) The transmission ratio P z / P 1 of the external sound pressure P and internal sound pressure P of the above-mentioned acoustic circuit is as shown in Figure a). Become,
When the acoustic Q is high, the resonance characteristics become steep as in real records,
When the acoustic Q is low, the resonance characteristics become slow as shown by the dotted line.

The vibrator 24 outputs a signal voltage v8 due to the sound pressure difference between the sound pressure P directly received from the outside and the sound pressure P transmitted inside through the acoustic circuit, so it has characteristics as shown in Fig. 81b),
When the acoustic Q is high, the signal voltage near the cutoff frequency changes largely as shown by the dotted line, and when the acoustic Q is low, the change is small as shown by the dotted line.

When an acoustic circuit is used in this way, by setting the operating frequency band higher than the cutoff frequency fc, a signal voltage proportional to the external sound pressure P can be obtained, and various signals including hydrostatic pressure at a frequency sufficiently lower than the cutoff frequency fc can be obtained. For dynamic pressure, the internal and external pressures of the vibrator 22 are equal, and the vibrator 24
prevent mechanical damage.

[Problem that the invention seeks to solve]

However, this type of acoustic circuit basically has the following problems.

Suppose that the cutoff frequency is I KHz (D) Considering a high frequency acoustic circuit, the volume of the cavity is, for example, 1ooCrn3.
Assuming that the cross-sectional area of 5 is 11 mm, the length of the metal tube when filled with acoustic oil is approximately α57 mm, and 7
Can be made with a through hole in the lunge. However, with the above specifications, the length of the metal tube of a low frequency acoustic circuit with only the cutoff frequency lowered to 10 Hz is approximately 5.7 m, which is extremely long.

Even if such long metal tubes are wound in a spiral manner, they cannot be wound with a small curvature in order to prevent the inner diameter from collapsing, resulting in large winding dimensions and poor workability.

Furthermore, if the volume of the cavity is kept constant and the cutoff frequency is lowered, the acoustic Q will increase as is clear from equation (4), and the frequency characteristics of the signal voltage, that is, the reception sensitivity - frequency characteristics of the acoustic transducer will change. It also has the drawback of giving abrupt changes. In the above example, the acoustic Q at a cut-off frequency of 10 Hz is 100 times the acoustic QO at a cut-off frequency of IKHz.

Another object of the present invention is to provide an acoustic circuit for an underwater acoustic transducer that eliminates the above-mentioned drawbacks and does not require a long metal tube.

[Means for solving problems]

The acoustic circuit of the present invention provides an underwater acoustic circuit that imparts an acoustic filter characteristic to the underwater acoustic transducer that is smoothed and set by an open metal tube that is provided so as to protrude into the sound field from the sealed inside of the transducer of the underwater acoustic transducer. In an acoustic circuit for a transducer, a groove having a continuous linear shape and length of a predetermined shape is provided, and then a plurality of elastic bodies are connected directly or through a support structure so that the grooves are connected. In this case, the device is configured to include acoustic filter characteristic imparting means for forming an acoustic path equivalent to the acoustic path of the open metal tube through this coupling and imparting predetermined acoustic filter characteristics.

[LOL example]

Next, the present invention will be explained in detail with reference to the drawings.

Figure 1 shows underwater acoustics using the acoustic circuit of the present invention, and
The acoustic circuit 3, the acoustic circuit 4, and the diaphragm 7 are connected to the fixture 6.
They are attached to the top and bottom of the body 2.

The pores providing acoustic inertance are configured as a series of paths from the through hole 2a of the membrane body 2 to the groove 3b and the through hole 3a of the acoustic circuit 3, and the groove 4b and the through hole 4a of the acoustic circuit 4. , the acoustic oil 8 is filled up to the inside of the internal color diaphragm 7 of the body 2.

The acoustic circuit 3 has a continuous groove formed in an elastic body of a predetermined shape such as a disk, and the shape can be selected from, for example, a sinusoidal waveform, a spiral shape, a spiral shape, or any other arbitrary shape. can be used. The purpose of this groove is to seal it by some means and use it as an acoustic path similar to a thin metal tube, so the cross-sectional area and length can be changed as desired as long as they match the purpose of use. It is possible to use a shape of . 'In the case of figure M1, the disc-shaped acoustic circuits 3 and 4 with such grooves are closely connected,
The through hole 42 is fixed in a laminated manner from the joint with the through hole 2a.
A series of paths including this will function equivalently to a metal tubular tube having a length greater than or equal to this.

When the underwater acoustic transducer shown in FIG.
Through each through hole 4a, 3a of the acoustic circuit 4.3 and each groove 4
b, 3b and the through hole 2af of the transparent body 2, but the sound waves above the cutoff frequency are attenuated by an acoustic filter made up of the acoustic inertance due to the pores and the acoustic compliance inside the housing before reaching the back surface of the transducer l. However, it does not affect the driving force from the outer surface of the vibrator l, and as a result, the vibrator l performs acousto-electrical conversion corresponding only to the vibration force from the outer surface.

Also, changes in hydrostatic pressure that are sufficiently lower than the continuous frequency are not attenuated by the acoustic filter, so the same pressure changes are applied to the outer and back surfaces of the transducer l, resulting in mechanical protection of the transducer l. .

In the acoustic circuit shown in FIG. 1, the acoustic circuit 3 is a first elastic body, and the acoustic circuit 4 is a second elastic body, and these two elastic bodies are in close contact with each other and are laminated. The second embodiment is also included.

FIG. 2 is a sectional view showing both a third embodiment and a fourth embodiment of the present invention.

A cylindrical vibrator 9 is supported by a column 10 and an acoustic circuit 11, 7'), and 12 and 13, and the two flange 13 is further provided with an acoustic circuit 14.Acoustic circuit 1 of FIG.
1 and 14 utilize the acoustic circuit according to the fourth embodiment of the present invention in which a screw-shaped groove is provided on the circumference of a cylinder, and a diagonal column 10° flanges 12 and 13 are used to cover this groove. metal gaskets 17a, 17b, 17c, 17d for improving adhesion between the flange 12 and the cap 16;

176 is embedded.

A large depression is provided inside the acoustic circuit 14 to provide acoustic compliance characteristics.

In the configuration of FIG. 2, an acoustic compliance is created between the vibrator 9 and the column lO, and the acoustic inertance provided by the through hole 10a of the column, the groove 11b of the acoustic circuit, and the pore of the through hole 11a is connected to the acoustic inertance 7. Lunge 120 through hole 12
at'' to the acoustic compliance created between the flange 12 and the cap 16.

Furthermore, the acoustic circuit 11 (DX through hole 11 a' and 7 lunges 1
Through the acoustic inertance of the through hole 13a of No. 3, the acoustic compliance between the acoustic circuit 14 and the flange 13, and the acoustic inertance of the groove 14b of the acoustic circuit 14 and the through hole 14a, the connection is made to the external sound field. A path from the inside of the diaphragm 19 fixed by the fixture 15 to the vibrator 9 is filled with acoustic oil 8.

The acoustic compliance group and the acoustic inertance group shown in Fig. 2 also operate as an acoustic filter in the same way as in Fig. 1. It is a top view which shows the structure of the 5th Example of this invention.

FIG. 3 shows a spiral groove 20 on the plane of a disc-shaped elastic body 20.
b, and a through hole 20m provided at one end of this groove, and FIG. Groove 2
1b and a through hole 21a provided at one end of this groove. Fig. 5 is a partial structural diagram showing the 70th embodiment of the present invention.

In the seventh embodiment shown in FIG. 5, a magnetic material penetration part 22t is provided in the through hole 13a of the seven flange 13 shown in FIG. 2, and this penetration part is filled with a magnetic fluid 23t. By adopting such a structure, the acoustic inertance of this part is increased due to the attractive force between the penetration part 22 and the magnetic fluid 23, and by selecting a conductive material pipe for the penetration part 22, the inside of the penetration part 22 is increased. Acoustic resistance can be provided by eddy current loss. With the structure shown in Figure 5, it is possible to lower the acoustic Qt of the acoustic inertance, and as a result, the characteristics change at the high cutoff frequency of the acoustic filter is slowed down, and as a result, the acoustic transducer has a smooth receiving sensitivity-frequency characteristic. give.

This magnetic fluid 21 acts as described above for the minute sound waves of the signal, but it also acts against pressure 9 that exceeds the sealing force of the magnetic fluid 23, such as changes in the volume of acoustic oil due to changes in hydrostatic pressure or changes in temperature. However, once the seal by the magnetic fluid 21 is broken and the pressure is removed, it returns to its original state due to the properties of the magnetic fluid. It is effective even when used in part or all of the recess, and the acoustic resistance can be increased by mixing conductive fine powder or hollow spheres with the magnetic fluid. These can be easily implemented as the eighth and ninth embodiments of the present invention, respectively.

〔Effect of the invention〕

As explained above, according to the present invention, by closely laminating elastic bodies having densely packed grooves and through holes, it is possible to construct a low frequency acoustic filter in a small size and with good workability.

Furthermore, by integrating a large number of acoustic circuits with so-called acoustic elements such as acoustic compliance, acoustic inertance, and magnetic fluid acoustic resistance into nine layers, an acoustic circuit for an underwater sound transducer that easily adjusts the characteristics of an acoustic filter has been realized. I can see the effect of being able to do it.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the first and second embodiments of the present invention, FIG. 2 is a cross-sectional view showing the third and fourth embodiments of the present invention, and FIG. FIG. 4 is a plan view showing the fifth embodiment of the present invention; FIG. 4 is a plan view showing the tX6 embodiment of the present invention; FIG. 5 is a partial sectional view showing the seventh embodiment of the present invention; FIG. 7 is a cross-sectional view showing an example of a conventional high-frequency/deep-depth acoustic circuit, FIG. 7 is an electrical equivalent circuit of the acoustic circuit shown in FIG. 6, and FIG. The resonance characteristic diagram of the circuit, FIG. 8(b), is the vibrator string force signal voltage characteristic diagram of the acoustic circuit shown in FIG. l... vibrator, 2... living body, 2a
...Through hole, 3...Acoustic circuit, 3a.
...Through hole, 3b...Groove, 4...
・Acoustic circuit, 4a...Through hole, 4b...
・Groove, 5, 6... Fixture, 7... Diaphragm, 8... Acoustic oil, 9... Vibrator, 10...・Strut %1Oa...Through hole, 11...Acoustic circuit, lla, iia'...
...Through hole, 11b...Groove, 12.13...
7 langes, 12a, 13m...through hole, 14...acoustic circuit, 14a...through hole, 14b...groove, 15. ·····Fixture,
16...Cap, 17a-17e...
・Metal packing, 19...Indentation, 19...
...Diaphragm, 20...Elastic body, 20a
...Through hole, 20b...Groove, 21...
...Elastic body, 21a...Through hole, 21b.
... Groove, 22 ... Penetration part, 23 ...
...Magnetic flow material, 24... Vibrator, 25...
...Strut, 26...7 lunge, 26a...
...Through hole, 27...Metal tube, 28...
・7 Lunge〇) ““2.ノ' Difference 1 Time leather 3 Fig. 4 Fig. $8 (L) TM

Claims (9)

[Claims] (1) In an acoustic circuit for an underwater acoustic transducer, the underwater acoustic transducer is provided with acoustic filter characteristics set in advance by an open metal tube provided so as to protrude into the sound field from the sealed inside of the transducer of the underwater acoustic transducer, A plurality of elastic bodies provided with grooves having a continuous line shape and length of a predetermined shape are coupled directly or through a support structure such that the grooves are connected, and in this case, this coupling causes acoustic vibration of the open metal tube. 1. An acoustic circuit for an underwater acoustic transducer, comprising an acoustic filter characteristic imparting means for forming an acoustic path equivalent to the path and imparting predetermined acoustic filter characteristics. (2) a first elastic body having a groove having a predetermined length and a through hole provided at one end of the groove; the first elastic body being overlapped with the first elastic body to cover the groove; and a second elastic body having a through hole that passes through a part of the groove while overlapping the elastic body and covering the groove, or a second elastic body having the groove provided with the through hole. An acoustic circuit for an underwater acoustic transducer, characterized in that the second elastic body is laminated in close contact with the body. (3) The first or second elastic body includes an elastic body having a recess, the groove, and a through hole provided at one end of the structure as an entrance and exit of the recess. 1) The acoustic circuit for an underwater acoustic transducer according to item 1). (4) The groove provided in the first and second elastic bodies is formed as a screw-like structure on the circumference of the elastic cylinder. Acoustic circuit for underwater acoustic transducer. (5) The acoustic circuit for an underwater acoustic transducer according to claim (1), wherein the first and second elastic bodies are elastic plates provided with spiral grooves on a plane. . (6) Claim (1) provides that the first and second elastic bodies are provided with grooves concentrically arranged on the plane of the elastic plate and connected to each other alternately from left to right.
Acoustic circuit for underwater acoustic transducer as described in . (7) Underwater acoustics according to claim (2), characterized in that at least one of the groove and the through hole is made of a magnetic material, and the magnetic material portion is filled with a magnetic fluid. Acoustic circuit for transducer. (8) An acoustic circuit for an underwater acoustic transducer according to claim (3), characterized in that at least one of the depression and its entrance/exit is made of a magnetic material, and the depression is filled with a magnetic fluid. . (9) Claim No. (7) characterized in that conductive fine powder or hollow spheres are mixed into the magnetic fluid.
The acoustic circuit for an underwater acoustic transducer as described in Sections and (8).